Stripper actuating mechanism for differential pressure forming machines



April 9, 1968 G. w. BROWN STRIPPER ACTUATING MECHANISM FOR DIFFERENTIAL PRESSURE FORMING MACHINES Filed Aug. 22, 1966 3 Sheets-Sheet l FIG! INVENTOR. GAYLORD W. BROWN Apnl 9, 1968 G. w. BROWN 3,376,607

STRIPPER ACTUATING MECHANISM FOR DIFFERENTIAL PRESSURE FORMING MACHINES Filed Aug. 22, 1966 5 Sheets-Sheet FIG 2 INVENTOR GAYLORD W BROWN April 9, 1968 G. w. BROWN STRIPPER ACTUATING MECHANISM FOR DIFFERENTIAL PRESSURE FORMING MACHINES Filed Aug. 22, 1966 5 Sheets-Sheet i FIG 3 l Illlllllllllllll INVENTOR. GAYLORD W. BROWN afearman E# me Unite States Patt 3,376,667 Patented Apr. 9, 1968 3,376,607 STRWPER ACTUATING MECHANISM FOR DIF- FERENTIAL PRESSURE FORMEWG MACHINES Gaylord W. Brown, Beaverton, Mich., assigner to Brown Machine Company of Michigan, Inc., Beaverton, Mich., a corporation of Michigan Filed Aug. 22, 1966, Ser. No. 573,916 7 Claims. (Cl. 18-19) This invention relates generally to stripping mechanism for differential pressure forming machines and more particularly to mechanism incorporated therein for automatically withdrawing a stripper plate following a predetermined delay during which the mold with which it coopcrates is partially withdrawn. In present day differential pressure thermo-plastic plastic forming machines a stripper plate is associated with the female mold assembly and operates to initially hold the plastic web when the female mold is being withdrawn to strip the formed plastic articles therefrom. Once the formed articles have been fully separated from the mold cavities, the stripper plate itself is retracted. In conventional practice, fluid pressure operated cylinders are provided to operate the stripper plate and require, of course, connections to a source of fluid under pressure and timing mechanism for insuring that the stripper plate is operated at the proper time.

One of the prime objects of the present invention is to utilize linkage mechanism already existing in such machines for automatically actuating stripper retracting linkage and withdrawing the stripper plate at the proper time so as to render unnecessary such former fluid pressure systems and the timing mechanisms associated therewith.

Another object of the invention is to provide positively operating stripper plate withdrawing mechanism of highly reliable character which operates simply and economically to perform its function.

Other objects and advantages of the invention will be pointed out specicially or will become apparent from the following description when it is considered in conjunction with the appended claims and the accompanying drawings, in which:

FIGURE l is a fragmentary, perspective elevational view of a differential pressure forming machine which incorporates the invention;

FIGURE 2 is a transverse, sectional elevational view taken on the line 2-2 of FIGURE l;

FIGURE 3 is a greatly enlarged, sectional side elevational view showing the actuating pin in engagement with an abutment member provided on the stripper retracting linkage;

FIGURE 4 is a fragmentary, end elevational view of the stripper retracting linkage at a time when the stripper plate and mold are in fully extended forming position;

FIGURE 5 is a similar view at a time when the mold has been withdrawn and the stripper plate is about to be retracted;

FIGURE 6 is a similar view at a time when the stripper plate is being retracted; and

FIGURE 7 is a similar view at a time when the mold assembly has been substantially fully withdrawn.

Referring now more particularly to the accompanying drawings, wherein is shown differential pressure forming apparatus of the nature of the machine shown in the present assignees copending application Ser. No. 293,959, entitled Diiierential Pressure Forming Machine, a letter F generally designates the frame of the machine which is shown as having side members 10' connected by an upper channel-shaped member 11 and a lower inversely dis posed, channel-shaped member 12. Mounted in fixed position on the upper frame 11 is a double-acting, iluid pressure operated cylinder 13 having a piston rod 14 which is coupled at its lower end, as at 15, to an upper platen frame generally designated 16. As shown, the platen frame may comprise end members 17 and 18 connected by side members 19 and 20. The members 17 and 18 are also braced by intermediate cross members 21 and 22.

Mounted on the platen assembly 16 is a female mold box assembly generally designated 23 which includes female mold members 24 supported from the top wall 25 of the hollow assembly 23 by bolts 26. The mold assembly 23 is supported at its corners from the platen |16 by clamp plate members 27 secured by bolt members 28 and includes a stripper plate 29 which is independently supported in a manner which will be presently described. The female mold members 24 comprise separate cup-shaped inserts which extend freely through openings 30 in the stripper plate 29. The inserts also extend through and are sealed in openings 31 provided in the lower wall 32 of the mold assembly box 23, and a vacuum line 33 leading from a suitable source of vacuum, such as a motor operated vacuum pump, communicates with the female mold members 24 in the usual manner, such as through ports 34 provided therein.

The frame portion 12, shown in FIGURE 2, similarly supports a double-acting, uid pressure operated cylinder 35 having a piston rod 36 which couples at 37 to a lower platen assembly 38 which, as shown, may be formed similarly to the upper platen assembly 16. Similar clamp plates 39 secured by bolts 40 clamp a hollow male mold box assembly generally designated 41 to the end rails 42 and 43 of the lower platen assembly 38. As FIG- URE 2 particularly indicates, the mold box assembly 41 includes an air manifold or air box 44 having ports 45 therein which assist in the forming operation in the manner described in the aforementioned copending application. An air line 46 may be provided in communication with a suitable source of air under pressure to provide air to the box 44 at the proper time. Also mounted by the air box 44 in vertical -alignment with the female mold members 24 are plug assist members 47 which, in the usual manner, are employed to initially deform the heated plastic web P and facilitate its entry into the female mold members 24.

The stripper plate 29 is mounted for movement independent of the mold assembly 23 and is wtihdrawn only after the female mold assembly 23 has been moved a predetermined distance upwardly. Rod members 48 extending freely through openings 49 in the vacuum box central post supports 50 are connected to cross bars 51 as shown, there being coil springs 52 provided between the cross `bars 51 and the upper wall 25 of vacuum box assembly 23. The cross bars 51 connect support frame members 53 which are suspended by means of toggle linkage mechanisms generally indicated at 54 at each corner from support block members 55 which are xed to the upper frame channel member 11. Each linkage mechanism 54 includes at its upper end a pair of links 56 which at their upper ends are connected by a pin S7 to one of the support blocks 55 and also includes a link 58 which is connected between links 56 by a pivot pin 59 and is connected at its lower end to the members 53 by a pivot pin 60.

As in the aforementioned application, the forming machine illustrated employs toggle linkage systems for locking the platens in molding position and exerting a preloading stress thereon urging the molds 23 and 41 in a direction toward the plastic sheet P during the molding operation. Outboard of the blocks 55 are support blocks 61 in vertical alignment with support blocks 62 mounted on cross braces 63 provided on the upper platen assembly 16. A double-acting, fluid pressure operated cylinder 64 at each end of the upper platen 16 is supported at its outer end between the blocks 61 and 62 by pairs of straddling toggle links 65 and 66 which pivotally connect to t-he cylinder at their converging ends at 67 and are pivotally connected to the blocks 61 and 62, respectively, by pins 68 and 69. The piston rod 70 of each cylinder 64 connects with a block 71 and each block 71 is pivotally connected to toggle links 72 and 73 by a pivot pin 74. The lower platen assembly includes identical linkage mechanism in which identical parts have been given the same numerals except that the numerals have been primed, and these parts need not be independently described.

It has been discovered that the toggle linkage associated with cylinders 64 can be employed to operate the stripper 29 and eliminate the considerable mechanism formerly necessary to do this job. Mounted between each pair of stripper supporting toggle links 56 at each side of the machine is a bar 75 which, as indicated in FIGURE l, mounts spaced apart abutment blocks 76 and 76a. Each pair of blocks 76 and 76a are actuated by pin 74, which has an extending end 74a projecting inwardly between each pair of blocks 76 and 76a, as shown in FIG- URES 1 and 3-7. The specific construction of each actuator block 76 is illustrated more particularly in FIG- URE 3 and, as shown, includes a bore 77 within which is disposed a coil spring 78 and a pin member 79 having a conical end. The edges of the bore 77 are swaged inwardly, as at 80, to prevent the pin 79 from being inadvertently withdrawn from the bore 77. One or more clamp bolts 81a may be used to adjustably secure the block in place and extend through elongated slots 81 provided in the block 76. The construction of blocks 76a is identical and the pins 79 similarly extend toward pin ends 74a. The pin springs 78 have, of course, much less strength than the springs 52 mounted on the stripper support rods 49. The purpose of the spring positioned pins 79 is to provide a certain operating tolerance. -It is desired that the links 56 and 58 be in vertical alignment when the vacuum box assembly 23 and stripper 29 are in down or fully extended position. It is also desirable that the stripper 29, when it returns to the vacuum box 23, move up into snug engagement with vacuum box 23, and the pin ends 74a must not prevent this from happening. FIGURES 4-7 particularly illustrate the operation of the linkages 54. FIGURE 4 shows the links in a position in which the mold box assembly 23 and stripper 29 are in fully down position and the pin end 74a is slightly compressing pin spring 78. In FIGURE 6 the pin end 74a has fully engaged the block 76a, compressed the spring 78 therein, and slightly moved the links 56 and 58. The usual clamp plate assembly comprising perimetral clamp plate 82, which is connected by brackets 83 to the piston rods 84 of pressure tiuid cylinders 85, is employed in the well-known manner fully described in the aforementioned copending application.

In operation, and assuming the platens 16 and 38 and the mold members which they support are originally in withdrawn position and a heated plastic sheet has been indexed to a position between the mold assemblies 23 and 41, cylinders 13 and 64 are operated in the rst place to respectively move the platen 20 downwardly and expand links 72 and 73 from a contracted, buckled position to the position in which they are shown in FIGURES 1 and 2. In this position the links 72 and 73 are in vertical alignment and the pin 74 is on center to lock mold 23 in position and exerts a preloading force on the platen 20 urging it in a direction toward the plastic sheet P. The pin ends 74a during this time move from the position shown in FIGURE 7 to the position shown in FIGURE 4 and are operated to expand the links 56 and 58 to the vertically aligned position in which they are shown in FIGURES 1, 2 and 4. In thus moving the stripper plate 29 downwardly with the mold assembly 23 to engage the plastic sheet P, the springs S2 are compressed as shown in FIGURE 2.

The cylinders and 64' are then operated to move the male mold assembly 41 upwardly to respectively engage the plastic sheet P and expand the links 65 and 66'` sheet P distended by the plug assists 47 into intimatev engagement with the cavities of the female mold inserts 24.

Thereafter, cylinders 64 and 13 are actuated to respectively withdraw the mold assembly 23 and buckle the4 links 72 and 73. Initially, the pin ends 74a simply move in the space between abutments 76 and 76a from the position shown in FIGURE 4 to the position shown in FIG- URE 5 and during this time the stripper plate 29 remains in engagement with the plastic sheet P as the mold assembly 23 is withdrawing therefrom. When the pin ends 74a do contact the abutments 76a and buckle the links 56 and 58, as in FIGURE 6, so that the pins 59 move out of center position, the compressed springs 52 are free to rapidly expand and bring the stripper plate 29 sharply up into engagement with the female mold assembly 23. The cylinders 35 and 64 are also operated to respectively withdraw the mold assembly 41 and buckle the links 72 and 73.

The spring mounted pins provide a tolerance which eliminates the need for precise positioning of the blocks 76 and 76a. For instance, it is quite ditlicult to so position the abutments 76 and 76a so that the pins 59 are moved to center position by abutments 76a when the stripper plate 76a in such position that they are disposed rearwardly of the blocks 76 far enough to let the stripper plate 29.` come all the way back into tight engagement with mold assembly 23 when the stripper plate 29 is permitted to return. The spring pressed projections 79 in blocks 76a prevent the blocks 76a from obstructing the return of the stripper plate 29.

It is to be understood that the drawings and descriptive matter are in all cases to be interpreted as merely illustrative of the principles of the invention rather than as limiting the same in any way, since it is contemplated that various changes may lbe made in the various elements to achieve like results without departing from the spirit of the invention or the scope of the appended claims.

I claim:

1. In a dilferential pressure forming machine: frame means; a pair of opposing mold members supported thereby, at least one of which is mounted to be moved relatively toward the other to Ian extended Aposition adjacent a deformable plastic sheet therebetween; said movable mold member having cavity means to receive the plastic sheet therein; means creating a differential pressure on opposite sides of said plastic sheet to draw the sheet into intimate contact with said cavity means; stripper plate means associated with said movable mold; support means supporting said stripper plate means for movement independently of the movable mold and operable to effect withdrawal of said stripper plate means; and means hav-` t ing a lost motion connection with said support means operated when said movable mold is being withdrawn 1 from the plastic sheet, and only after a predetermined withdrawal thereof, to actuate said means supporting said stripper plate means and withdraw said stripper plate means.

2. The combination detined in claim 1 in which said support means comprises expansible and contractile linkage mechanism.

3. The combination defined in claim 1 in which said means having a lost motion connection with said support means comprises mold locking toggle links operated by fluid pressure operated cylinder means to expandand 29 is down and still position the abutments urge said movable mold toward the other mold and having an actuating part operable to actuate said support means when said toggle links are contracted.

4. The combination defined in claim 1 in which said support means comprises expansible and contractile toggle linkage supporting said stripper plate means from said frame means; spring means compressed when said toggle linkage is expanded and said movable mold is in extended position substantially engaging the plastic sheet; spaced apart abutments are provided on said toggle linkage; and said means having `a lost motion connection includes a projecting part extending between said abutments and movable in a path of travel from one to another.

5. The combination defined in claim 4 in which said abutments have yieldably mounted pins projecting therefrom in a direction toward said projecting part.

6. The combination defined in claim 4 in which said means having a lost motion connection with said support means comprises toggle links for locking said movable mold in extended position and said projecting part comprises the extending end of a pin pivotally connecting the toggle links.

7. The combination defined in claim 4 in which said projecting part moves said toggle linkage to on center position when said movable mold and stripper plate are moved to substantially engage the plastic sheet.

References Cited UNITED STATES PATENTS 1,415,018 5/1922 Coates. 1,880,858 10/1932 Davis. 2,962,758 12/ 1960 Politis. 3,007,201 11/1961 Brummer. 3,115,678 12/1963 Keen etal. 3,166,790 1/1965 Keyes. 3,180,776 4/1965 Hessel. 3,189,399 6/1965 Jacobs etal.

20 WILLIAM I. STEPHENSON, Primary Examiner. 

1. IN A DIFFERENTIAL PRESSURE FORMING MACHINE; FRAME MEANS; A PAIR OF OPPOSING MOLD MEMBERS SUPPORTED THEREBY, AT LEAST ONE OF WHICH IS MOUNTED TO BE MOVED RELATIVELY TOWARD THE OTHER TO AN EXTENDED POSITION ADJACENT A DEFORMABLE PLASTIC SHEET THEREBETWEEN; SAID MOVABLE MOLD MEMBER HAVING CAVITY MEANS TO RECEIVE THE PLASTIC SHEET THEREIN; MEANS CREATING A DIFFERENTIAL PRESSURE ON OPPOSITE SIDES OF SAID PLASTIC SHEET TO DRAW THE SHEET INTO INTIMATE CONTACT WITH SAID CAVITY MEANS; STRIPPER PLATE MEANS ASSOCIATED WITH SAID MOVABLE MOLD; SUPPORT MEANS SUPPORTING SAID STRIPPER PLATE MEANS FOR MOVEMENT INDEPENDENTLY OF THE MOVABLE MOLD AND OPERABLE TO EFFECT WITHDRAWAL OF SAID STRIPPER PLATE MEANS; AND MEANS HAVING A LOST MOTION CONNECTION WITH SAID SUPPORT MEANS OPERATED WHEN SAID MOVABLE MOLD IS BEING WITHDRAWN FROM THE PLASTIC SHEET, AND ONLY AFTER A PREDETERMINED WITHDRAWAL THEREOF, TO ACTUATE SAID MEANS SUPPORTING SAID STRIPPER PLATE MEANS AND WITHDRAW SAID STRIPPER PLATE MEANS. 